1. Field of the Invention
This invention relates to a printer apparatus.
2. Related Background Art
A known type of fully-multiple recording head employed in a color printer has line heads units 1A, 1B, 1C and 1D for applying four colors: Yellow, Magenta, Cyan, Black, which are disposed in that order with the unit 1A in the lower most position in the direction of paper supply, as shown in FIG. 1. A sheet of recording paper 2 is transferred over this recording head (a head assembly having head units) in the direction indicated by the arrow A in FIG. 1 to perform recording.
TOF marks 3 are disposed on the sheet of recording paper 2 at predetermined intervals. The position from which recording of batch of data corresponding to each page of recording paper is commenced is set on the basis of each TOF mark 3. The TOF marks 3 are detected by a TOF sensor 4 (only one position of a TOF photosensor is exemplified in FIG. 1) which is disposed under the head assembly. Recording is started from each predetermined position marked on the recording paper 2 when the TOF mark 3 is detected by the TOF sensor 4.
If there is some error in the placement of the TOF sensor 4 relative to the recording head as shown in FIG. 2, namely, a deviation .delta. from the normal position S in the direction of paper supply (the same would be true in the reverse direction) during the recording of color images or color graphs which are displayed on a monitor screen such as CRT are recorded, this deviation causes a TOF deviation.
The TOF deviation results in a deviation of the position of an image recorded on the recording paper 2. Therefore, such deviations must be minimized.
Also, any mechanical deviation in the longitudinal. direction of the recording paper from the standard position of the head unit, e.g., a deviation in the longitudinal direction of the recording paper, causes a deviation of color registration, or the spatial relationship between the desired image on the recording medium and a color image actually recorded thereon in the longitudinal direction.
Similarly, a mechanical deviation in the transverse direction of the recording paper from the standard position S of each head unit, e.g., a widthwise deviation, causes a widthwise deviation of registration.
If one or more of the head elements 1A to 1D (one or more) moves out of the standard positions and there are amounts of mechanical misalignment relative to these standard positions, these amounts of misalignment also cause misalignment of the registration.
It has been difficult for the conventional method to reduce the TOF deviation or deviations in the longitudinal or widthwise direction of the recording paper to adjust the head alignment.
It has also been difficult for a new head assembly (recording heads or head units) to be suitably adjusted with respect to the TOF deviation, deviations in the longitudinal or widthwise direction of the recording paper, and the head alignment at the time of replacement of the head assembly.